The present invention relates to a pump aggregate of the type comprising a driving motor with a rotatable drive shaft and a pump, as e.g. a gas compressor, of the piston type which is driven by the driving motor.
In known designs of this type the pump piston is usually driven by a crank shaft connected to the driving motor and a connecting rod. In addition to those bearings required for journalling the crank shaft, such a design requires two bearings namely one between the connecting rod and the crank shaft, and a second one between the connecting rod and the piston pin. Since the last mentioned bearing is situated inside the piston lubrication problems arise in a compressor designed to deliver oil free air.
In the present invention, which is defined in the appended claim 1, a single-row spherical ball bearing is used as the only bearing in the transformation of the rotational movement of the drive shaft of the driving motor into a reciprocating movement of the pump piston. This bearing is furthermore situated outside the piston so that no lubrication inside the piston is needed.